OEM Exhaust Manifolds Looking for some other info

[wdoc15]

I need to change my Manifolds, Risers and Elbows in a 5.7 350 Mag Horizon

In Brazil original ones costs US$ 4k, I found a OEM company that mades OEM weldered version for 1.3k USD
Looking more opinions.
It's made of carbon steel 1/4"
No coated protection inside or outside, just a normal black paint.
My Questions:

1) The weld maybe crack due to high temps, leaks from the plates junctions.
2) Insuficient Water Flow, he said that his version offers more water flow, this can be or not a good thing.
3) Lack of Curves inside maybe cause bad water flow

Water only join gases at final end of the elbow.
I will cut in half my old Mercury original manifold in order to compare, but if anyone has already cutted, please post some pictures.

 

[alldodge]

Your motor was be way below the water line to need that much rise

If your in salt water I doubt the manifolds will last very long being steel.

The Mans have restriction if for any other reason they are tall. The restriction is a good thing depending on how much just to make sure to keep Mans full of water.

 

[cyclops222]

You appear to be showing different manifolds. 1 looks like it is sheet metal riser held together wit just a few tack welds. Do not buy them if they really look like that picture.

 

[wdoc15]

Explaining
Black ones are finished units,
Inside 1 picture is the middle man, after assembled will look like Internal3 and then they weld
I will visit in person this company to learn more, still not a believer on the ideia.

 

[wdoc15]

Your motor was be way below the water line to need that much rise

If your in salt water I doubt the manifolds will last very long being steel.

The Mans have restriction if for any other reason they are tall. The restriction is a good thing depending on how much just to make sure to keep Mans full of water.

Original engine was mounted with the 3" risers, I understand is a good thing in having more water in the manifolds, so colder temps.

 

[Scott Danforth]

Original engine was mounted with the 3" risers, I understand is a good thing in having more water in the manifolds, so colder temps.

you must not understand why risers are used. it is specifically to make sure the top of the elbows are above the static water line so your boat doesnt sink or fill the motor up with water when at rest.

 

[cyclops222]

Another reason is with a fully loaded boat. If you suddenly go from Fast on plane speed to neutral ? The motor stalls out unexpectedly. The stern will drop down. And the following wake will run up the back side of the boat. Possibly going into the engine. Causing the very bad hydro / water locking of the pistons. Been on a boat that I had to remove all the sparkplugs & crank out the water spray. Some people asked if the boat was going to sink.

 

[wdoc15]

Another reason is with a fully loaded boat. If you suddenly go from Fast on plane speed to neutral ? The motor stalls out unexpectedly. The stern will drop down. And the following wake will run up the back side of the boat. Possibly going into the engine. Causing the very bad hydro / water locking of the pistons. Been on a boat that I had to remove all the sparkplugs & crank out the water spray. Some people asked if the boat was going to sink.

I understand, 20 years in boats, never make sudden stops, you need to decrease slowly and then stop, otherwise pocket $$$$ will sufer.

 

[wdoc15]

I got some pictures of a 5 years used manifold from the guy, much better then my original ones.

 

[Scott06]

I got some pictures of a 5 years used manifold from the guy, much better then my original ones.
View attachment 405641

The rust on inside of exhaust port is usually a sign of internal leaking, water gets in engine via exhaust valves

 

[Lou C]

I was thinking the same thing! They shouid be tested with Acetone then you’ll know for sure they don’t leak…

 

[wdoc15]

yeah, but 5 years and it's better than a original one. My concerns still not about price but water flow, gas flow, too cold water that can cause engine below 90C.
I resolved to buy and test witha thermal camera, but need some reference from one with Mercury original.